New, larger quantum-dot window steps out of lab

By Tereza Pultarova

Published Thursday, October 13, 2016

American engineers have created the first reasonably-sized quantum dot window that can generate electricity using the energy from the Sun.

The technology, described in the latest issue of the journal Nature Energy, is the first quantum dot window of a size that could actually be used in a building. Previously, only palm-sized demonstrators have been created.

“We are developing solar concentrators that will harvest sunlight from building windows and turn it into electricity, using quantum-dot based luminescent solar concentrators (LSC),” said Victor Klimov, lead scientists at the Los Alamos Center for Advanced Solar Photophysics (CASP).

“Semitransparent LSCs can also enable new types of devices such as solar or photovoltaic windows that could turn presently passive building facades into power generation units.”

LSC consist of a slab of transparent glass or plastic coated with highly emissive fluorophores. The technology can collect solar energy from a large area and re-emit photons at lower energy convenient for photovoltaic cells located around the collectors’ edges.

To create a window of the size described in the article, the researchers used a technique known as ‘doctor-blade’. The technique enables depositing thin layers of dot/polymer composites on top of glass panes. The technique, which was originally developed for printing, uses a blade to wipe excess liquid material from the surface. The result is a thin and uniform coating evenly covering the pane.

To create the demonstrator, the researchers have used colloidal quantum dots – semiconductor spheres with a core of one material and a shell of another. The dots have nearly 100 per cent emission efficiency and don’t deteriorate when exposed to sunlight. Moreover, the absorption and emission spectra of the dots can be tuned almost independently by varying the size and/or composition of the core and the shell. This allows the emission spectrum to be tuned by the parameters of the dot’s core to below the onset of strong optical absorption, which is itself tuned by the parameters of the dot’s shell. As a result, loss of light due to self-absorption is greatly reduced. “This tunability is the key property of these specially designed quantum dots that allows for record-size, high-performance LSC devices,” Klimov said.

The researchers believe that the technology could cut the cost of solar energy generation in future.